I'm probably starting to stretch the analogy a bit thin but: In Australia, similar issues, but we've been doing back-burning/fuel-reduction-burns for quite a few years now to deal with these problems (the indigenous population practiced controlled burns for a variety of purposes well before whitefellas arrived). However, some evidence is now starting to emerge that the mode controlled burns is effecting the long term ecology of the forests, and favouring certain species over others, and preventing the build-up of larger, less-flammable trees.

So, to tie it back to IoT: Would a 'controlled burn' (i.e. a bot which bricks vulnerable devices) only destroy the low hanging fruit (i.e easily exploitable devices) and leave the harder vulnerabilities in place, building up for the bigger fire in a years time?